Stabilizing a silver halide emulsion hardened with formaldehyde and mucochloric acid



United States Patent ()fifice 3,295,981 Patented Jan. 3, 1967 3,295,981 STABILIZING A SILVER HALIDE EMULSION HARDENED WITH *FORMALDEHYDE AND MUCOCHLORIC ACID Kirby M. Milton, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Jan. 12, 1965, Ser. No. 425,064 9 Claims. (Cl. 96109) This invention relates to photographic elements, more particularly photographic silver halide emulsions containing fog inhibiting agents and hardeners.

For most photographic applications adequate levels of hardness for the gelatin-silver 'halide photographic emulsions must be maintained. Also it is desirable in such emulsions to have present substances which act as fog inhibitors and stabilizers therein. Ordinarily, photographic emulsions on storage tend to lose sensitivity and become developable without exposure to light. In the processing of photographic emulsions it is important that the emulsion layer maintain satisfactory physical strength so as to resist physical and environmental degradation. Urazole has been considered a very satisfactory additive to photographic emulsions to exert a stabilizing and fog inhibiting effect thereon.

Mucochloric acid has found wide acceptance in the photographic art as a hardener for photographic emulsions because it is less toxic and less volatile than other hardeners such as formaldehyde and also has less propensity to cause fog in photographic emulsions. However, the use of urazole with a mucochloric acid hardener tends to eliminate substantially all of the advantages produced by either compound utilized alone in a photographic emulsion.

One object of my invention is to provide photographic emulsions containing both a urazole type antifoggant and an aldehyde type hardener in which neither detracts from the effectiveness of the other. Another object of my invention is to provide gelatin-silver halide photographic emulsions containing a stabilizer of the urazole type and as the hardener therein a mixture of mucochloric acid and formaldehyde in proportions in which the advantages of each are utilized. Other objects of my invention will appear herein.

I have found that by using the combination of mucochloric acid and formaldehyde as the hardener in a photographic emulsion that in combination with a urazole type antifoggant there appears to be produced almost synergistic effects in regard to emulsion stabilization and hardness, especially during storage. These synergistic effects are noted in photographic silver halide emulsions coated on either cellulose ester supports or on dimensionally stable polyethylene terephthalate film supports.

As the stabilizer or antifoggant, compounds which'may be used as antifoggants in accordance with my invention are cyclic hydrazides have the following formula wherein Z represents the atoms required to complete a heterocyclic ring, such as and R and R each are selected from the group consisting of H, alkyl, such as methyl, ethyl, propyl, butyl, amyl, octyl, decyl and dodecyl, substituted alkyl, such as carboxyethyl, sulfopropyl or sulfobutyl, aryl, such as phenyl or naphthyl, and substituted aryl, such as benzyl; and monoacyl and dlacyl derivatives of compounds having the above general formula, such as the monoand di-acetyl, propionyl, butyryl, valeryl, caprylyl, capryl and lauryl derivatives of such compounds. Typical specific useful compounds having the above general formula include urazole, 4-phenyl urazole, l phenyl urazole, 4-et hyl urazole, maleic acid hydrazide and phthalic acid hydrazide. The structural formula of the monoacyl and diacyl derivatives of compounds having the above general formula is not known; specific useful examples of such compounds are diacetyl derivatives of urazole and 4- phenyl urazole. A method for preparing the latter compounds is described in Chemical Abstracts, volume 50, page 12033.

The hardening'agent employed is a mixture of mucochloric acid and formaldehyde, the formaldehyde being at least 5% and no morethan 40% of the hardener which is used. Using less than 5% formaldehyde the urazole interferes with the hardening action of mucochloric acid while if the hardener is composed of more than 40% formaldehyde the objectionable features of formaldehyde in considerable proportions become evident to a pronounced degree. The hardener is used in the emulsion in an amount within the range of 0.15%, based on the weight of the gelatin in the emulsion as a rule, although any hardening amount of the mixture of mucochloric acid and formaldehyde will have a hardening effect on the gelatin.

Urazole and antifoggants of the urazole type exert an antifogging effect in a photographic emulsion in most any concentration. Ordinarily the urazole compound will be used in my invention in an amount within the range of 0.55% based on the weight of the gelatin in the silver halide emulsion.

The following examples illustrate more specifically the invention:

Example 1 To a negative speed silver bromoiodide emulsion of which approximately 3.6 molar percent of the silver halide was silver iodide was added mucochloric acid at the rate of 1.0 part per 168 parts of gelatin. The emulsion was divided into samples and these samples were further treated as described below and then were coated on polyethylene terephthala-te film support at a coverage of 760 mg. of silver and 835 mg. of gelatin per square foot. The percentage swell of the dry coatings when placed in distilled water was obtained for each with the following results.

Percent swell Feature: in water A. Control (contains mucochloric acid) 320 B. Control+1.0 part urazole per 119 parts of gelatin 490 C. Control+ls0 part of urazole+.5 part formaldehyde :per 119 parts of gelatin 260 Each of the film samples were exposed, developed, fixed and dried and were tested as freshly prepared and after storage for a week at 120 F. It was found that in the case of the film samples without urazole appreciable fogging took place, whereas using urazole in combination with mucochloric acid and formaldehyde hardener in the emulsion not only was swelling in water kept to a minimum but no appreciable fogging effect was obtained.

Example 2 A coarse grain silver bromoiodide photographic emulsion of the X-ray type was coated on film support after the addition of 0.2855 part of mucochloric acid per'l39 parts of gelatin in the emulsion. Various emulsion samples were taken and various addenda were added in accordance with the following table. The various samples of emulsion were coated onto film support at a coverage of 454 mg. of silver and 584 mg. of gelatin per square foot. The samples were processed and the percentage of swell obtained in the developer was observed. The results obtained were as follows.

Film samples were also photographically tested particularly after storage at 120 F. It was found that the samples containing both urazole and mucochloric acidformaldehyde hardener had good stability and as shown by the table above exhibited good resistance to swelling by aqueous solution showing the effectiveness of the.

hardener therein.

Example 3 An emulsion as referred to in Example 2 was coated onto film support after adding mucochloric acid as referred to in that example. Various emulsion samples were taken, addenda were added in accordance with the following table, and the samples were coated onto cellulose acetate film support at a coverage of 454 mg. of silver and 584 mg. of gelatin per square foot. The thickness of the coatings before and after soaking in water at room temperature was determined in each case and the percent vertical swell in water are given in the following table.

Percent vertical Feature: swell in water H. Control (contains mucochloric acid) 464 mole+0.2 g. formaldehyde/Ag mole 316 Example 4 Samples were prepared and coated onto cellulose acetate film support as described in the preceding example. The samples obtained were processed and the percent .of swell in the developer was observed. The addends and the results obtained in the case of each with and without formaldehyde were as follows:

. Percent vertical swell in developer 0. Control (contains mucochloric acid) 254 P. Control+2.19 g. 1-acetyl-4-phenyl 'urazole/Ag mole 252 Q. Control+2.19 g. 1-acetyl-4-phenyl urazole/Ag mole+0.2 g. formaldehyde/Ag mole 206 R. Control (contains mucochloric acid) 276 S. Control+1.54 g. maleic hydrazide monoacetate/ Ag mole 294 T. Control+l.54 g. maleic hydrazide monoacetate/ Ag mole +0.2 g. formaldehyde/Ag mole 259 U. Control+1.l2 g. succinic hydrazide/Ag mole 303 V. Control-1.12 g. succinichydrazide/Ag mole +0.2 .g. formaldehyde/Ag mole 266 W. Control+2.13 g. 4-octyl urazole/Ag-mole 260 X. Control+2.l3 g. 4-octyl urazole/Ag mole+0.2 I

g. formaldehyde/Ag mole 234 The invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected with the spirit and scope of the invention as described hereina-bove, and asdefined in the appended claims.

I claim:

1. A light sensitive gelatin-silver halide emulson containing as a hardener therein a mixture of mucochloric acid and formaldehyde, the latter constituting 5-40% of the mixture and as an antifoggant therein a compound selected from the group consisting of compounds having the following general formula:

wherein Z represents the atoms required to complete a heterocyclic ring and R is selected from the group consisting of H, alkyl and aryl; and the monoacyl and diacyl derivatives of compounds having the above formula. 2. The emulsion of claim 1 in which the antifoggant is urazole. I

3. The emulsion of claim 1 in which the antifoggant is amino phthalic hydrazide.

4. The emulsion of claim 1 in which the antifoggant is acetamido phthalic hydrazide.

5. The emulsion of claim 1 in which the antifoggant is dilauramidophthalhydrazide.

6. The emulsion of claim 1 in which the antifoggant is l-acetyl-4-phenyl urazole.

7. The emulsion of claim 1 in which the antifoggant is maleic hydrazide monoacetate.

8. The emulsion of claim 1 in which the antifoggant is succinic hydrazide.

9. The emulsion of claim 1 in which the antifoggant is 4-octyl urazole.

No references cited.

NORMAN G. TORCHIN, Primary Examiner. J. H. RAUBITSCHEK, Assistant Examiner, 

1. A LIGHT SENSITIVE GELATIN-SILVER HALIDE EMULSON CONTAINING AS A HARDENER THEREIN A MIXTURE OF MCOCHLORIC ACID AND FORMALDEHYDE, THE LATTER CONSISTITUTING 5-40% OF THE MIXTURE AND AS AN ANTIFOGGANT THEREIN A COMPOUND SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS HAVING THE FOLLOWING GENERAL FORMULA: 